The present invention relates to a countersunk hole reinforcing structure, in which the wall body of the top recess of the countersunk hole is reinforced by reinforcing ribs.
When fastening a plate member to an object by screw bolts, countersunk holes may be provided at the plate member for the mounting of screw bolts. However, when a countersunk hole is made, the wall thickness is relatively reduced at the countersunk hole, and the wall body of the top recess of the counter sunk hole tends to be damaged during installation of the screw bolt.